Sometimes it is necessary in real estate disputes to provide the value of real estate. Obviously, opinions and values can vary wildly. The “fair market value” of real estate is generally what a “willing buyer would pay in cash to a willing seller.” Labrayere v. Bohr Farms, LLC, 458 S.W.3d 319, 330 (Mo. 2015). An expert opinion as to what this is must be based on substantial data, not mere conjecture, speculation or unwarranted assumption. Glaize Creek Sewer v. Gorham, 335 S.W.3d 590, 594 (Mo. Ct. App. 2011). Notably, an owner of real estate may testify as to the value of the real estate — even when he or she does not necessarily have any formal training or certifications in real estate valuation. Section 490.065.3, RSMo.